In recent years, the prevalence rate of psychiatric disorders has increased due to the stress resulting from, for example, interpersonal relationship, economic problems, environmental destruction, and pollution problems. In certain psychiatric disorders, an excitement of dopaminergic nervous system is considered to be involved and therapeutic agents including antipsychotic agents have been used for the treatment. Antipsychotic agents currently used in clinical practice are classified roughly into two groups, typical antipsychotics and atypical antipsychotics. Typical antipsychotic agents exhibit their therapeutic effects through the inhibitory activity against the dopamine receptor, but also show side effects such as extrapyramidal symptom. Atypical antipsychotics, also called as SDAs (serotonin-dopamine antagonists), have the inhibitory activity on the serotonin receptor as well as the dopamine receptor and show fewer side effects than the typical antipsychotics. However, even atypical antipsychotics can not be completely free from side effects.
The effect of atmospheric ion on a living body has been attracting attention for many years. “Atmospheric ion” is a generic name of charged particles floating in the air. The atmospheric ion is classified into large ion and small ion, wherein the small ion has greater effects on a living body. The small ion is generated from disruption of water droplets which occurs around a waterfall and a stream in nature. Such phenomenon is called as waterfall effect (or Lenard's effect). The small ion is also produced by, for example, radiation of cosmic ray or from radioactive substances, electrolytic dissociation of atmospheric components occurring in lightning or corona discharge, or radiation from a radon hot spring. The small ion is a ultrafine particle being nanometer (nm)-order (10−3 μm or less) and can be classified into positive air small ion (presumed chemical formula: H3O+·(H2O)n) and negative air small ion (presumed chemical formula: O2−·(H2O)n). The negative air small ion is shown to significantly reduce the levels of dopamine and serotonin in blood which have been increased with physical exercise, during the recovery period from fatigue after the exercise (Non-patent literature 1). The negative air small ion is also considered to affect a living body by donating an electron (e−) (Non-patent literature 2).
The negative air small ion is produced in nature and therefore it is not necessary to worry about the side effect on a living body. In order to benefit from the effect of the negative air small ion continuously, however, people have to live near a waterfall, or to always take a radon hot spring, which may restrict their living environment. Further, a negative air small ion generator utilizing water drop dissociation is not portable.
Non-patent literature 1: “Physiological effects of negative ions in the atmosphere on recovery from fatigue after exercise”, Ryushi et al., Japanese Journal of Clinical Ecology, Vol. 6, No. 1 (1997)
Non-patent literature 2: “Effects of negative air ions to inhibit aggregation of erythrocytes”, co-authored by Yamada and Chino, IGAKU TO SEIBUTUGAKU, Vol. 141, No. 3 (2000)